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TPS61085EVM-355: Prototype tests

Part Number: TPS61085EVM-355
Other Parts Discussed in Thread: PMP9770

Hello,

We need to know if its possible to obtain another voltage values changing some electronic components to test and evaluate the TPS61085EVM-355 module.

We read the PMP9770 reference document. But we dont know if the circuit design have limitations about the output voltages.

We need these values:

AVDD = 8.2V

VGH = 22V

VGL = -7V

VCOM = 3V

Cheers,

Daniel Matias.

  • Hi Daniel,

    TPS61085EVM-355 is the evaluation board only for boost converter. By changing the feedback resistors R1/R2, you can get the desired output voltage.

    PMP9770 is a reference design based on boost converter. Two charge pump circuits are added here. The AVDD is set to 10V. VGH charge pump doubles AVDD, which is 20V output. And VGL charge pump circuit generates the negative AVDD, which is -10V. D2 is a 18V zener diode, and D3 is a 7.5V zener diode. Considering the Vbe of transitor, customer could get 17V and -7V.

    Your desired output voltage could be got by adding another charge pump circuit because VGH is close 3 times of AVDD. If you are interested, I can draw the circuit for you.
  • Hi Zack,

    Thanks for the considerations. I think with the new LCD that we defined yesterday, we have a more easy situation.

    Above the real voltages that we need:

    AVDD: 8.0 up to 8.4 volts;

    VGH: 18 up to 20 volts;

    VGL: -9 up to -7 volts;

    VCOM: 3.0 up to 3.4 volts.

    We will very grateful if you help us with this quest.

    Could you provide the circuit design to us?

    Thanks,

    Daniel.

  • Hi Daniel,

    AVDD is set to 8.4V by changing upper feedback resistors to 94kohm. Using two charge pump circuit and a 20V zener diode to get 18-20V VGH. The negative charge pump circuit will generate the -7V VGL. By changing potentiometer R6 you could get 3-3.4V VCOM. 

    Based on the zener diode you chosed, you may need to change R5 value. You could refer to PMP9770 user's guide to guidence.

  • Hi Zack,
    Thanks for the support! I will execute the changes in the circuits.
    Regards,
    Daniel